Known commercialized lithium ion batteries use several types of transition metal oxide compounds such as lithium cobalt dioxide (LiCoO2), lithium nickel dioxide (LiNiO2), and lithium manganese dioxide (LiMn2O4) etc. as the material for the positive electrode. LiCoO2 is the most commonly used material. Although the overall properties of LiCoO2 are the best, its cost is high and, due to its scarcity, the cost is likely to rise even higher. Its supply could even dry up. Therefore, many countries are researching the use of at least two of the following transition metals: Cobalt (Co), Nickel (Ni), and Manganese (Mn) as the basic ingredient for compounds of lithium transition metal oxide to be used for electrodes in batteries. Representative relevant work includes: Reference 1: Zhaolin Lin et al. in J. Power Sources, 88-82 (1999) 416-419 which discloses the synthesizing method for the lithium transition oxide compound, Li Ni1-x-yCoxMnyO2; and Reference 2: Chinese Patent No. CN1271185A, Oct. 25, 2000, which discloses a method of preparation for an additive ingredient, LiCoO2, LiNiO2, and LiMn2O4.
The inventors of this invention found that, when compared with oxidized compounds prepared by thermally decomposing the mixture made by combining the salts or hydroxide compounds of transition metal elements such as cobalt, nickel, and manganese and with salt of lithium, the compounds prepared by the method described by Zhaolin, Lin, et al. in reference 1 have better distribution of grain diameter, density, and electrochemical capacity. However, in order to have said excellent properties, the range of the distribution of the diameter for the spherical intermediate products formed using method reported by Zhaolin, Lin, et al in reference 1, Ni1-x-yCoxMny(OH)2, has to be narrow. This can only occur by strictly controlling the precipitation conditions which is difficult to accomplish in practice. The method described in Chinese Patent No. CN1271185A (reference 2) spray mixes soluble salts, carbonates, or alkaline solutions of lithium and transition metals such as of cobalt, nickel, or manganese, and alkaline carbonates to obtain a crystal compound; then decompose thermally to obtain LiCoO2, LiNiO2, and LiMn2O4 as the additive ingredient. However, this method is not easy to implement as the Li2CO3 produced has a large solubility, and some of it is dissolved and removed during the rinsing process to remove the negative ions. This decreases the lithium content of the final product and results in the inability to obtain the amount calculated from the formulas of LiCoO2, LiNiO2, and LiMn2O4.
Due to the limitation of the prior art, it is therefore desirable to have novel and innovative methods for the preparation of compounds of lithium transitional metal oxide.